Building a powerful loudspeaker enclosure was always a part of my plans but I was reading many negative comments about 15" drivers. One of them was about their cone mass affecting to their transient response. Later on, I have read the article on Adire Audio and I have realized that the rise time has nothing to do with the cone mass but the inductance of the voice coil. When the inductance of the voice coil is low, the speaker can drive more power from the amplifier and at this very moment the mass of the cone becomes negligibly small. After finding out that fact I've started searching for a 15" woofer with small mH. Interesting enough, drivers with Neodymium magnets do have low inductance value as compared to others. The inductance of those drivers can be small as 0.6mH or 0.8mH which is as small as a driver inductance with a radius of 16cm. During my search I have found out that 18Sound has proper speaker units (15NLW9500). I have bought a pair and I also purchased an active cross-over (Dahlquist). I have calculated and built a proper enclosure for 18Sound drivers and adjusted the cross-over point and levels.

This became an extremely powerful design. The full-range unit redeems you from all the setbacks of using a 15" driver in the system. Because, when you use a 15" driver, due to its' limited bandwith, you have to go for a 3 way system and this means that your cross-over will be a complex one. Also, you have to deal with tweeter and midrange units. But, by using a full-range driver, the system becomes a two way enclosure, which is much easier to design and tune. Besides, since there are no fragile units in the system like dome tweeters or mid-range drivers, the enclosure can handle much more power as compared to a 3 way system. I believe this is one of the best sounding enclosures that I have built.

I have used 2 Radford STA-25 Series III amplifiers. One amplifier for woofers and one for full-range units. The cross-over was tuned to 150Hz and I had to lower the gain of the full-range unit by 6dB. I have tuned the enclosure to 40Hz and I could be able to achieve a flat response to 37Hz, which was more than enough for my listening room.